1. Field of the Invention
The present invention relates to a method and apparatus for stopping power supply in a radio frequency identification (RFID) system, and more particularly, to a method and apparatus for determining whether a battery included in a RFID tag is powered using a continuous wave signal and a command signal of a RFID reader.
The present invention was supported by the IT R&D program of Ministry of Information and Communication Republic of Korea (MIC). [2005-S-106-02, Development of Sensor Tag and Sensor Node Technologies for RFID/USN]
2. Description of the Related Art
Conventionally, in a radio frequency identification (RFID) technique, tags are attached to respective objects, and unique identifications (IDs) in the tags are wirelessly recognized so that corresponding information included in the tags can be collected, stored, processed, and traced in order to provide a service in terms of the locations of the objects, a remote processing, management, and information exchange between the objects.
As a replacement of conventional barcodes, the RFID technique of using tags is applied to various fields such as from material management and distribution to security. Therefore, it is expected that the RFID technique will become a new market in the industry.
RFID systems can be classified according to how readers and tags communicate with each other, whether the tags are powered, and where the frequency bandwidth the readers and tags use is. The readers and tags are either mutually inducing a method or an electromagnetic method depending on how the readers and tags communicate. The readers and tags are either battery-powered or passive according to how the tags are powered. The readers and tags operate in a long middle, short, ultra-short, or extremely ultra-short range according to their frequencies. A variety of types of standards of RFID systems are established or are currently being established.
FIG. 1 is a block diagram of a conventional passive RFID tag. Referring to FIG. 1, the conventional passive RFID tag, which is not powered, that uses a reflective wave of an RFID reader includes an RF antenna 101, a voltage booster 102, an electrically erasable programmable read-only memory (EEPROM) 103, a demodulator 104, a controller 105, and a modulator 106.
The conventional passive RFID tag, which is not powered, operates the EEPROM 103 and the controller 105 using an output voltage of the voltage booster 102 (W) that increases the power of an electronic wave received through the RF antenna 101. When the RFID reader and the conventional passive RFID tag are far away from each other (for example, by more than 5 m), the conventional passive RFID tag cannot generate the voltage necessary for operating the EEPROM 103 and the controller 105. In more detail, the recognition distance of the conventional passive RFID tag is limited to about 5 m, and the recognition information on the conventional passive RFID tag is unreliable if the conventional passive RFID tag is attached to a metal object.
Thus, active and semi-active tags are battery-powered, and thus, the active and semi-active tags have a longer recognition distance than the conventional passive RFID tags and can be applied to more applications than passive tags, however, the active and semi-active tags suffer from a limited battery lifespan.